1. Field of the Invention
The present invention relates to polymers of vinyl monomers, which contain, as monomer units, substituted styrenes with at least 3 fluorine atoms, a process for their preparation and their use as optical material for the production of optical systems.
2. Discussion of Prior Art
Optical systems, for example lenses for photographic cameras, have already been produced from transparent plastics. Only thermoplastics have practical significance, because they can be processed rationally and considerably better than glass. Polymethyl methacrylate is in an exceptional position because it is the only thermoplastic to be employed industrially, instead of silicate glasses or low refractive index, for the production of converting lenses.
Polystyrene, styrene/acrylonitrile copolymers and bisphenol A polycarbonates are also customary (Plaste und Kautschuk 19, 41-44 (1972)), and are employed exclusively for dispersing lenses. These materials either have the combination of a low refractive index and a small dispersion (equivalent to a high Abbe number), such as, for example, polymethyl methacrylate, or the combination of a high refractive index and a high dispersion (equivalent to a low Abbe number), such as polystyrene or aromatic polycarbonates.
In the calculation of optical systems, for example systems of lenses for cameras, it is not possible to predetermine certain image properties and to calculate refractive indices, optical dispersions and geometric data of the system therefrom, but the converse procedure must be followed. The refractive indices, optical dispersions and geometric data are predetermined and the image properties are calculated therefrom. It is thus necessary to carry out many calculations and to vary the parameters systematically in order to arrive at a system which can be used for the intended purpose. Strict limitations are thus imposed, because favourable calculated systems can only be realized if the optical materials having the necessary refractive indices and optical dispersions are also available. There is thus a particular need for optical substances which can easily be processed, for example by thermoplastic shaping, and have other combinations of refractive index and optical dispersion than the materials hitherto known and accessible.